Bryan and Riordan had 90 pencils together. Bryan had 18 more pencils than Riordan. Both of them sold some of their pencils. Riordan sold 20% less pencils than what Bryan sold. In the end, Riordan had half as many pencils left as Bryan. How many pencils had Bryan left?
| |
Bryan
(1) |
Riordan
(2) |
Make p the same
(2)x2 = (3) |
Comparing Bryan
and Riordan at first |
18 more |
|
|
| Before |
54 |
36 |
72 |
| Change |
- 5 u |
- 4 u |
- 8 u |
| After |
2 p |
1 p |
2 p |
Number of pencils that Riordan had at first
= (90 - 18) ÷ 2
= 72 ÷ 2
= 36
Number of pencils that Bryan had at first
= 36 + 18
= 54
Number of pencils that Riordan sold in percent
= 100% - 20%
= 80%
80% =
80100 =
45 Make p the same.
(1) = (3)
54 - 5 u = 72 - 8 u
8 u - 5 u = 72 - 54
3 u = 18
1 u = 18 ÷ 3 = 6
Number of pencils that Bryan had left
= 54 - 5 u
= 54 - 5 x 6
= 54 - 30
= 24
Answer(s): 24
